In copending U.S. application Ser. No. 955,060 filed Oct. 26, 1978 by Ulrich D. Geissler, et al. for "Blood Compatible Polymers and Medical Devices Made Therefrom" it is taught that, most surprisingly, common plasticizers for plastic materials such as di-2-ethylhexylphthalate and di-2-ethylhexyladipa e are anti-hemolytic agents. In their presence, stored blood exhibits significantly lowered hemolysis over the period of storage than in the absence of such materials.
While the commercially-available blood bags have been made of polyvinyl chloride formulations which include di-2-ethylhexylphthalate, other candidate blood bag materials were free of such ester-type plasticizers, intentionally so, because it had been suggested from some experts that the ester-type plasticizers were undesirable, and should not be present in the plastic containers used for storage of blood.
It most surprisingly turned out that the various materials which were free of the ester-type plasticizers exhibited an undesirably high plasma hemoglobin content after, for example, 21 days of storage, indicating that the lysis rate of the red blood cells was high.
After this phenomenon was identified, further studies indicated that it was apparently necessary to ncorporate the ester plasticizer into plastic material in contact with the stored blood, to get the anti-hemolytic effect. This could be done either by formulating the material into the blood container itself, or a plastic insert member to the container in which the insert member contains the ester-type plasticizer in accordance with copending U.S. patent application Ser. No. 954,969, filed Oct. 26, 1978 by Henry W. Collins and entitled "Blood Bags Having an Insert Member", which application is assigned to the assignee of this application.
The initial research, however, also indicated that the addition of quantities per se of the liquid ester material such as di-2-ethylhexylphthalate to the blood container did not exhibit the anti-hemolytic effect obtained when the ester material is incorporated into the plastic material of the blood container or an insert within the container. Attempts to emulsify the ester material were also unsuccessful, resulting in emulsions that were basically unstable.
By this invention, it has been surprisingly found that stabilized emulsions of anti-hemolytic agents as described herein provide further significantly improved antihemolytic effect, when placed in the presence of stored blood, to make it possible to even reduce the hemolysis of stored blood to less than that which is conventional for the commercially-available, ester-plasticized polyvinyl chloride blood bags. The emulsion may be stabilized in accordance with this invention by a specific technique as described below.